The present invention relates to waste disposal and more particularly to waste disposal employing plasma flame.
The use of plasma flame to heat or disintegrate material has been known and used for some time.
The advantage of a plasma flame in such an application is the intense heat that can be generated (ie, 10,000 C), and when applied to any material, will cause complete dissociation of the compounds. As applied to certain waste materials, such as medical waste, it assures the absolute destruction of any form of organic residue, additionally, it melts dangerous sharp objects and glassware, producing an atomically clean residue. By atomically clean is meant that by complete plasma treatment, the resultant products comprise substantially only atomic elements in vapor form. By-products of a plasma fired disintegrator can be controlled by appropriate means to consist of simple elemental gases, carbon, metals, and environmentally safe compounds.
A number of disadvantages of utilizing a plasma flame to destroy waste products have prevented or limited its use. The plasma flame is very small compared to the bulk of material that is to be treated. This requires extensive pretreatment of the waste products, such as the need to compact, pulp, and/or shred the material to reduce it to a suitable size that the flame can handle prior to feeding the products to the flame plume. In the case of hazardous waste, the pre-treating apparatus will become contaminated, thus increasing the problems involved in handling such materials.
Another problem associated with present plasma systems is that the nozzles are subjected to accelerated erosion requiring frequent and extended periods of down time to replace the nozzles. When air is employed as the plasma gas, the presence of oxygen contributes significantly to the erosion problem. If another gas is employed, such as nitrogen, to avoid the presence of oxygen, this increases the costs substantially and renders the system less competitive than other waste disposal systems.
A number of United States Patents have been issued which describe the use of plasma for the destruction of waste products.
U.S. Pat. No. 4,509,434 discloses a plasma waste disposal system utilizing an oxidizing agent intended for fluid waste. It refers to combustion products and there is no provision for handling solid waste.
U.S. Pat. No. 4,630,555 shows an incinerating process using a nozzle for injecting pure oxygen and a liquid, maintaining a temperature between 600.degree. C. and 1000.degree. C. The process does not use a plasma flame and its primary goal is to control combustion products by controlling temperatures.
U.S. Pat. No. 4,770,109 teaches a complex arrangement for applying a plasma flame to a large area of waste material by rotating the waste material chamber under the plasma flame generator. This patent also requires pre-digesting the material to feed into the chamber.
U.S. Pat. No. 4,831,944 describes a system in which a column of solid waste is consumed by ordinary combustion and the nonconsumable waste drops to the where it is further reduced by plasma flames. Oxygen is introduced to encourage combustion.
U.S. Pat. No. 4,980,092 teaches the destruction of cyanided organic and organo-chlorinated waste materials by shredding, pulping, and extruding the waste through a restricting orifice and feeding the product to the plasma flame. Contamination of the shredding apparatus would appear to be a significant unresolved problem.
None of the preceding teaches or suggests the present invention.